Potato and parsley soup with black pudding and cheddar toasties

By Jason Atherton From Saturday Kitchen Ingredients For the soup 700g/1lb 9oz Désirée potatoes, peeled and thinly sliced 50g/1¾oz unsalted butter 750ml/1¼ pints vegetable or chicken stock 150ml/5fl oz double cream 6 tbsp parsley oil (1 bunch parsley blended with 100ml/3½fl oz olive oil) …